Deflection pulley for a traction mechanism drive

ABSTRACT

The invention relates to a deflection pulley ( 1 ), intended for a traction drive, which includes a rolling-contact bearing as well as a ring body ( 4 ). A securing screw ( 8 ) as well as a spacer sleeve ( 9 ) serve as retaining elements. In order to provide a transport safety system ( 17 ), the spacer sleeve ( 9 ) is provided with at least one radial inwardly directed projection ( 18 ) which radially overlaps a threaded section ( 20 ) of the securing screw ( 8 )

FIELD OF THE INVENTION

[0001] The invention relates to a deflection pulley for deflecting a traction member, in particular a V-ribbed belt or a toothed belt of a traction drive. The deflection pulley includes a rolling-contact bearing with a non-rotatable inner ring and a rotating outer ring. The outer ring is hereby surrounded by a ring body which forms a pulley shell and has an outer surface area for guiding the traction member. Retainers and fasteners form together with the deflection pulley a unitary structure by means of a transport safety system.

BACKGROUND OF THE INVENTION

[0002] DE 297 20 776 discloses a deflection pulley having a grooved ball bearing which is surrounded on the outside by a molded-on pulley shell of plastic. The deflection pulley is secured by retainers comprised of a sealing disk and a screw which has a guide section received in the inner ring of the rolling-contact bearing of the deflection pulley. The outer circumference of the sealing disk forms at a same time a seal for the rolling-contact bearing. Provided in the center of the sealing disk is a cup-shaped stamped-in area having a cylindrical portion pressed into the bore of the inner ring of the rolling-contact bearing. The central bore of the sealing disk is provided to receive the guide section of the securing screw. The screw head is supported by an end surface of the inner ring by way of the sealing disk. The guide section extending from the screw head is provided to center the screw with respect to the inner ring of the rolling-contact bearing. To hold the retaining member captive and to secure it for transport, the sealing disk is provided adjacent the stamped-in area with elastic tongues distributed around the periphery and pressing at a slant in the axial/radial direction against the shaft of the securing screw. This transport safety system thus includes a sealing disk of complex configuration which incurs not only high manufacturing costs but complicates the installation.

SUMMARY OF THE INVENTION

[0003] Considering the drawbacks of the known solution, the object of the present invention is to provide a transport safety system which is cost-optimized and can easily be assembled while ensuring at the same time an effective captivation.

[0004] This object is attained in accordance with the invention by providing a spacer sleeve which is associated to the deflection pulley and formed with a through bore to receive the fastening screw and which includes a radially inwardly directed projection by which the fastening screw is secured in a force-fitting manner. Unlike the known prior art, this transport safety system according to the invention does not require an additional component and can be realized in a cost-efficient manner by means of a simple material shaping process. Moreover, the transport safety system according to the invention does not adversely affect in any way the assembly. Through appropriate configuration of the radial projection or several radial projections, the transport safety system according to the invention ensures further a positioning of the fastening screw in the spacer sleeve in correspondence with the installation position in the deflection pulley. This measure simplifies installation of the entire deflection pulley and permits at the same time an automated assembly of the deflection pulley as a consequence of the prefabricated arrangement of the fastening screw, including all retaining elements.

[0005] A further advantageous configuration of the invention involves the provision of radial projections distributed in symmetry about the circumference of the spacer sleeve. This measure improves the centered disposition of the fastening screw in the spacer sleeve.

[0006] Furthermore, the invention includes a spacer sleeve which has radial projections for implementing a force-fitting connection by extending them up to the outer surface area of the screw shaft. In this way, a clearance-free disposition of the fastening screw in the spacer sleeve can be ensured, accompanied with an exact alignment of the fastening screw in relation to the spacer sleeve. The force-fitting transport safety system provides at the same time for an improved positional fixation of all retaining elements during the transport and assembly of the entire unitary structure. Without additional components, a sufficient union of all retaining elements of the deflection pulley is ensured. The slightly increased tightening moment of the fastening screw as a consequence of the spot pressure applied radially on the screw shaft by the projections may, optionally, be compensated or corrected through a respectively increased tightening moment of the fastening screw.

[0007] The arrangement of the spacer sleeve and the fastening screw is so provided as to support the screw head of the fastening screw and the spacer sleeve on opposite end surfaces of the inner ring of the rolling-contact bearing. The fastening screw is hereby centered by the guide section press-fitted in the inner ring of the rolling-contact bearing as well as on the projections of the spacer sleeve via the screw section so that the installation position of the fastening screw is defined at the same time.

[0008] A further advantageous configuration of the invention provides an arrangement of the radial projections in a recess which is arranged in axially offset relationship to the end surface of the spacer sleeve. The position avoids any influence by the radial projections upon the terminal support surface of the spacer sleeve for example on a tension arm or on a contact surface of the internal combustion engine.

[0009] According to a further configuration of the invention, the spacer sleeve is designed as cast article and configured to include as blank already radial projections. A finished spacer sleeve that has been cast in this way saves a working step by which the projections have to be molded on through a swaging process. Fastening screws are used for such designed spacer sleeves with a shaft diameter which exceeds the diameter in the area of the threaded section.

[0010] Preferably, the radial projections have a half-round cross sectional shape. This shape is implemented through the use of respective tools by which material is shaped at an end surface of the spacer sleeve in the area of the central bore. The invention also includes projections of different design, of different geometric shape. The position of the radial projections enables their placement into the spacer sleeve after installation of the fastening screw, e.g. by means of a lathe center or other tool.

[0011] The spacer sleeve according to the invention is preferably made of aluminum or an aluminum alloy. As an alternative, the use of a spacer sleeve of steel may also be used, whereby a cutting or non-cutting manufacturing process may be applied.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will now be described in more detail with reference to the drawings, in which

[0013]FIG. 1 shows a longitudinal section of a deflection pulley which has integrated therein the transport safety system according to the invention;

[0014]FIG. 2 is an enlarged detailed illustration of an area marked “z” in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

[0015] The deflection pulley depicted in FIG. 1 includes a rolling-contact bearing 2 which is constructed as grooved ball bearing and has an outer ring 3 which is surrounded by a ring body 4 made of plastic. Guided on an outer surface area 5 of the ring body 4 is a traction member 6, constructed as V-ribbed belt. An inner ring 7 of the rolling-contact bearing 2 is connected with a retainer comprised of a fastening screw 8 as well as a spacer sleeve 9. The fastening screw 8 is supported via a screw head 10 on an end surface of the inner ring 7. A guide section 11 is placed axially adjacent to the screw head 10 and press-fitted in a central bore 12 of the inner ring 7. The spacer sleeve 9 is supported by the inner ring 7 on its end surface which is opposite to the screw head 10, whereby the spacer sleeve 9 has a guide collar 13 for centering on the inner ring 7 as well. The spacer sleeve 9 is provided with a through bore 14 for the fastening screw 8. On its end surface 15, which is distal to the rolling-contact bearing 2, the spacer sleeve 9 is stepped in the area of the through bore 14 and forms an axially offset recess 16.

[0016] In order to realize a transport safety system 19, which also serves to secure the assembly, the spacer sleeve 9 is provided with several circumferentially distributed projections 18 which extend radially in the direction of the fastening screw 8. These projections 18, preferably formed through material shaping, are associated to a screw shaft 19 of the fastening screw 8 and radially overlap a threaded section 20. As can be seen from FIG. 1, the fastening screw 8 has a screw shaft 19 with a diameter “d” which is smaller than the threaded section 20 of the fastening screw 8. As a result, a radial overlap is established between the transport safety system 17 and the threaded shaft 20 to effectively captivate the fastening screw. The radial projections 18 provided for the transport safety system 17 are introduced into the spacer sleeve 9 after the fastening screw 8 has been mounted. It is possible to cast a spacer sleeve 9, constructed as cast article, with projections 18. The finally cast spacer sleeve 9 thus requires no finishing operation in order to realize the transport safety system.

[0017]FIG. 2 shows more clearly the arrangement of the radial projections 18 by way of an enlarged illustration of the detail “z” in FIG. 1. Accordingly, the radial projection 18 is extended up to the screw shaft 19 of the fastening screw 8 and forms hereby a force-fitting connection or a press-fitted union. Thus, an intended positioning of the fastening screw 8 in relation to the spacer sleeve 9 and thus of the deflection pulley 1 is ensured, thereby simplifying the installation of the entire deflection pulley 1, for example to an internal combustion engine. FIG. 2 shows moreover a swaging 21 configured as a half-round recess on the spacer sleeve 9 for formation of the projection 19, by means of a local shaping of material. The radial projection 10 rests against the outer surface area of the fastening screw 8 in a force-fitting manner by way of a spot contact or line contact. As a consequence of the material elasticity and different material strength between the spacer sleeve 9, made preferably of aluminum, and the fastening screw 8 of steel, the projection 18 conforms to the outer surface area of the fastening screw 8 and deforms hereby. The force-fitting connection of the radial projections 18 on the screw shaft 19 effects a secure union of all components of the deflection pulley 1. This transport safety system 17 ensures integrity of all components of the deflection pulley 1 even during transport and enables a simplified assembly.

List of Reference Numerals

[0018]1 deflection pulley

[0019]2 rolling-contact bearing

[0020]3 outer ring

[0021]4 ring body

[0022]5 outer surface area

[0023]6 traction member

[0024]7 inner ring

[0025]8 fastening screw

[0026]9 spacer sleeve

[0027]10 screw head

[0028]11 guide section

[0029]12 bore

[0030]13 guide collar

[0031]14 through bore

[0032]15 end surface

[0033]16 recess

[0034]17 transport safety system

[0035]18 projection

[0036]19 screw shaft

[0037]20 threaded section

[0038]21 swaging 

1. Deflection pulley (1) associated to a traction drive, comprising: a rolling-contact bearing (1) with a non-rotatable inner ring (7) and a rotating outer ring (3), which is surrounded by a ring body (4) having an outer surface area (5) for guiding a traction member (6), and retaining means such as a fastening screw (8) received in the inner ring (7) for joining by means of a transport safety system (17) the deflection pulley (1) together with a spacer sleeve (9) to form a unitary structure, characterized in that the spacer sleeve (9) is provided as transport safety system with at least one radial inwardly directed projection (18) which secures the fastening screw (8) in a force-fitting manner.
 2. Deflection pulley according to claim 1, wherein the spacer sleeve (9) is provided with radial projections (18) symmetrically distributed about the circumference.
 3. Deflection pulley according to claim 1, wherein the fastening screw (8) is centered in the area of the screw head (10) by a guide section (11) press-fitted in the inner ring (7) of the rolling-contact bearing (2).
 4. Deflection pulley according to claim 2, wherein the radial projections (18) rest in a force-fitting manner on an outer surface area of a screw shaft (19) of the fastening screw (8).
 5. Deflection pulley according to claim 1, wherein the screw head (1) of the fastening screw (8) and the spacer sleeve (9) are supported on opposite end surfaces of the inner ring (7) of the rolling-contact bearing, and the transport safety system (17) defines an installation position of the fastening screw (8).
 6. Deflection pulley according to claim 1, wherein the radial projections (18) are arranged in a recess (16) disposed axially in relation to the end surface (15) of the spacer sleeve (9).
 7. Deflection pulley according to claim 1, wherein the spacer sleeve (9) is configured as cast article and provided as blank with radial projections (18).
 8. Deflection pulley according to claim 1, wherein the radial projections (18) are provided in the spacer sleeve (9), after mounting the fastening screw (8), by means of a material shaping process through swaging.
 9. Deflection pulley according to claim 1, wherein the radial projections (18) have a cross section of substantially half-round shape.
 10. Deflection pulley according to claim 1, wherein the spacer sleeve (9) is made of aluminum or an aluminum alloy. 